An image sensor, such as a metal-oxide-semiconductor (MOS) image sensor, is a device that converts an optical image into an electric signal and has been commonly used in the consumer electronics that require high resolution, such as digital cameras, apparatuses for applying personal communications service (PCS), game equipment, etc.
In order to realize higher resolution and satisfy the requirements of the consumer electronics. Pixel density of an image sensor may be increased and the size and pitch of the photoelectric transducer devices, such as photodiodes, that are involved in the image sensor may be shrank. However, the shrinkage in the pitch of the photoelectric transducer devices may cause electrical and optical crosstalk by which image resolution of the image sensor may thus be deteriorated; and the sensing images may be distorted.
In order to solve the problems, shallow trench isolation (STIs) disposed between two adjacent pixels have been applied to suppress the electrical and optical crosstalk. However, STIs cannot provide the image sensor enough barriers for electrical crosstalk suppression, especially in a backside illumination (BSI) image sensor, since the depth of the STIs is rather limited.
Therefore, there is a need of providing an improved image sensor and method for fabricating the same to obviate the drawbacks encountered from the prior art.